The purpose of this study is comparing the efficacy of tacrolimus and mycophenolate mofetil for the initial therapy of active lupus glomerulonephritis.

Patients with biopsy proven active lupus nephritis will be randomized to receive tacrolimus or mycophenolate mofetil, on top of corticosteroids, for initial treatment. Efficacy and adverse effects will be compared.

Inclusion Criteria:

1. Patients who fulfill at least 4 of the ACR criteria for SLE
2. Age >= 18 years
3. Biopsy proven active lupus glomerulonephritis (ISN/RPS class III/IV/V)
4. Serum creatinine < 200 umol/L at the time of randomization

Exclusion Criteria:

1. Patients who refuse to be randomized for treatment
2. Patients who prefer treatment with conventional agents such as oral or intravenous CYC for various reasons
3. Serum creatinine >= 200 umol/L at the time of randomization
4. Patients without renal biopsy or those who have lupus nephritis ISN/RPS class I,II,VI
5. Patients who are pregnant or plan for pregnancy within 12 months after randomization